December Great Story by Chris Sturken, 2016-17 Bay Area Climate Fellow
The Potty Plant Tour (As my dad would call it) 12/28
I arrived at Hayward’s Water Pollution Control Facility (WPCF) looking for answers to questions like–
“Is meter number 17P683 a smart meter?” and “Is the solar array grid-tied or building-tied?”–and received more than I bargained for. I smelled the not so sweet scent of sewage. David, on staff with the WPCF, showed me around the campus. I visited buildings you couldn’t hear in and others that I couldn’t breathe in, but it was one of the most fascinating tours I’ve ever been on!
Can you believe that Hayward’s WPCF processes ~11-12 MGD of “ya know”? And the WPCF does what nature would do on its own (treat wastewater) in only ~15 hours! Sludge goes in and clean water comes out, among other things I will share with you later.
There are so many steps that I can’t cover them all, but here are the ones that stuck with me the most: the sludge enters the Pump Station, then the Clarifiers, Trickling, Aeration Basins, Thickening, Digesters, and CoGen.
The Pump Station is deceptively large. It’s 3 stories tall! –But 2 of those stories are underground. There are 3 grinders which break-up the sludge. The Station also allows staff to remove ‘rags’ or clumps (of paper towels and other junk) that can clog the system. Tell your friends that if it’s plush, don’t flush. No paper towels, towelettes, etc.
Clarifiers allow solids to settle or float to the top, depending on their density. Those suspended solids are skimmed from the top by a rotating arm. It reminds me of my mom’s popcorn maker.
The skimmer rotates around, spreading the butter and mixing the popcorn kernels. Another way to explain a clarifier is this: it’s a giant bird bath. That is, lots of sea gulls enjoy the easy pickings (it’s nutrient-rich) and opportunity to bathe (ineffectively, to say the least).
Trickling is an interesting step in the process. It looks like a water tower from the side, but when you climb the precarious staircase (and don’t look down) to the top, you see a giant grate with another rotating arm spreading sludge-water. These grates are home to probably millions of microorganisms that break down that bad stuff further.
Aeration is just what it sounds like. The sludge-water is blown-up with air to give microorganisms the oxygen they need to do their job, which is to breakdown the matter. It looks like a giant hot-tub – just don’t go in it.
There’s a cyclical process that comes into play at this step. Some organisms, which have laid dormant, are reawakened after their release into the aeration pool. David described this as going out to a party on a party boat. They’re high on oxygen and chowing down. He said that they feel the same way some of us do after Thanksgiving dinner (if that is a tradition in your family).
The Thickening room has a conveyor belt (like at a grocery store checkstand). Here a polymer solution is spread over the moving sludge, acting as a binding agent to make it cling to itself more, therefore thickening it. Just a note about polymers: they are hydrophobic. In other words, they hate water. So they squeeze out excess water from the sludge.
The digesters are domelike, closed structures which harbor sludge for ~25 days. More microorganisms go to town breaking down the bad stuff. The primary purpose of this step, however, is to produce methane gas or biogas to fuel Hayward’s cogeneration engine and produces electricity.
Another source of fuel for the digesters is the FOG tank. This tank houses Fats, Oils, and Greases which are–I quote David here–the “red-bull for digesters”. This stuff will start your engine.
Here’s a little about the motivation behind David’s work.
He likes to keep things in perspective. In his view, if the organisms are happy, if all the conditions are right for them, he’s doing his job right and he’s happy. It’s all about the organisms and benefiting the environment for David.
Here’s a little about my experience.
David acknowledged my role in Hayward. He affirmed my presence there that day and all my questions by saying, “you’re here to help us”. I need that affirmation once in a while. I hope that you receive affirmation at work too.
Now, you’ll never look at the toilet the same again.